Known simply as “Jeb” and “Marco,” the men are longtime allies, friends and neighbors who live a five-minute drive from each other in bordering cities. Now the Miami-Dade GOP, built into a powerhouse by Bush in the 1980s, isn’t big enough for the two of them.

The family feud between these two titans of the Republican Party has loomed for months, during which GOP insiders from Miami to Tallahassee have dealt with it like many a conflicted family: with denial. Then it became indisputable Monday when Bush officially announced his bid — and his surrogates threw a few not-so-subtle jabs at Rubio for his lack of accomplishments and executive experience.

In one of the most politically dynamic counties in the most politically dynamic state, many Republicans say it will only get worse.

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The tensions and rumblings surrounding the question of who backs whom have ratcheted up as the polling margin between the two men has shrunk. The two are virtually deadlocked in Florida – a state that Republicans likely must win in order to carry the White House. Bush nominally leads Rubio among Florida Republicans, 20 percent to 18 percent — an inside-the-error margin — according to Quinnipiac University’s latest survey. Wisconsin Gov. Scott Walker comes in a distant third (out of 16 potential candidates) with 9 percent support.